Many NIA funded investigations use rodents to model aging processes and age-related diseases. Strict control of genetic purity, health ofthe animals including specific-pathogen-free status, and environmental variables is required to provide valid animal models that may be used to study the biological and behavioral processes in aging. Transgenic, knockout and mutant mice have added significantly to studies addressing specific questions or aspects of normal aging and age-related disease etiology. Sharing of genetically engineered and naturally occurring mutant mouse models between labs greatly enhances the research opportunities and generation of new information.